Effect Of Reaction pH Research Articles

Effects of reaction pH on regular nanorods and hierarchically structured β-Ga2O3 and their isopropanol sensing capabilities

Real-time detection of isopropanol is important for indoor air quality monitoring to improve human health. In this study, regular and hierarchical nanorod-based β−Ga2O3 morphological features were prepared using the microwave-assisted hydrothermal method following the variation of the reaction pH levels. A systematic study on their gas sensing performances was conducted to evaluate their potential as isopropanol gas sensing platforms. The sensor response and response times were directly controlled by morphology of β−Ga2O3. The randomly oriented β−Ga2O3 nanorods presented the highest response of 6.7 towards 90 ppm isopropanol while the β−Ga2O3 nanodandelions showed the fastest response/recovery times of 47/25 s. The observed variation in the gas sensing performances of the different β−Ga2O3 structures can be attributed to changes in morphological, textural, and compositional properties induced by the controlled reaction pH levels.

Effect of reaction pH on the microstructural, optical and electrical behaviour of ZnO/CuO heterostructured nanocomposite films

Effect of reaction pH on the microstructural, optical and electrical behaviour of ZnO/CuO heterostructured nanocomposite films

베타-아미노이소부티르산과 분지쇄 아미노산 함량이 증강된 닭가슴살 가수분해물의 제조: 프로테아제의 종류 및 가수분해 조건의 영향

Beta-aminoisobutyric acid (BAIBA) and branched-chain amino acids (BCAA) have recently received considerable attention because of their various health benefits. In this study, the hydrolysis characteristics of chicken breast for 11 commercially proteolytic enzymes were studied to evaluate the effect of protease type, reaction pH (5-8), leaction time (2-24 h) and enzyme concentration (0.25-8%), and the effect of two combined enzymes for the preparation of BAIBA- and BCAA-enriched chicken breast hydrolysates. The content of BAIBA was higher in hydrolysate by prozyme 2000P (38.72±3.01 mg/g, dry weight base), foodpro alkaline protease (30.24±2.54 mg/g) and alcalase (26.24±1.01 mg/g) while the BCAA content was higher in prozyme 2000P (108.96±2.63 mg/g), flavourzyme (81.12±4.78 mg/g) and sumizyme LP (62.88±3.83 mg/g). As the effects of reaction pH, time, and amount of added enzymes, the optimum condition for the preparation of BAIBA- and BCAA-enriched hydrolysates were as follows; reaction pH 6-7, reaction time 8-16 h and the amount of enzyme 4% (w/w) based on the dried chicken breast. However, no significant increase of BAIBA and BCAA content was observed when hydrolyzed with two combined enzymes. These results suggest that commercial proteolytic enzymes can be applied to prepare BAIBA- and BCAA-enriched chicken breast hydrolysates.

Inorganic phosphate self-sufficient whole-cell biocatalysts containing two co-expressed phosphorylases facilitate cellobiose production.

Cellobiose, a natural disaccharide, attracts extensive attention as a potential functional food/feed additive. In this study, we present an inorganic phosphate (Pi) self-sufficient biotransformation system to produce cellobiose by co-expressing sucrose phosphorylase (SP) and cellobiose phosphorylase (CBP). The Bifidobacterium adolescentis SP (BASP) and Cellvibrio gilvus CBP (CGCBP) were co-expressed in Escherichia coli. Escherichia coli cells containing BASP and CGCBP were used as whole-cell catalysts to convert sucrose and glucose to cellobiose. The effects of reaction pH, temperature, Pi concentration, and substrate concentration were investigated. In the optimum biotransformation conditions, 800 mM cellobiose was produced from 1.0 M sucrose, 1.0 M glucose, and 50 mM Pi, within 12 hr. The by-product fructose and residual substrate (sucrose and glucose) were efficiently removed by treatment with yeast, to help purify the product cellobiose. The wider applicability of this Pi self-sufficiency strategy was demonstrated in the production of laminaribiose by co-expressing SP and laminaribiose phosphorylase. This study suggests that the Pi self-sufficiency strategy through co-expressing two phosphorylases has the advantage of great flexibility for enhanced production of cellobiose (or laminaribiose).

Synthesis of gold nanoparticles using silk sericin as a green reducing and capping agent

Various natural materials were used recently for the synthesis of gold nanoparticles (AuNPs). These natural materials are attracting attention because they are more environmentally friendly than conventional chemicals used for AuNP synthesis. Silk sericin (SS) is a protein that is removed during the silk degumming process, and it has been studied for the synthesis of several inorganic materials, such as hydroxyapatite and silica. The present study synthesized AuNPs using SS. To optimize the conditions for the synthesis of AuNPs, the effects of reaction pH, SS concentration, reaction time and temperature during the formation of AuNPs were monitored using visual observation, a UV–Vis spectrophotometer, and energy-filtered transmission electron microscopy (EF-TEM) analysis. When the concentration of HAuCl4 was 1 mM, the optimal conditions for synthesizing AuNPs were an SS concentration of 1 mg/ml, a reaction pH of 7, a reaction temperature of 70 °C and a reaction time of 12 h. The AuNPs prepared under the optimal conditions had a size of approximately 17 nm, and the particles were well dispersed. When ethanol was added, the secondary structure of SS transitioned to β-sheets, the size of the gold nanoparticles increased to approximately 20 nm, and the amount of AuNPs increased. Amino acids bearing a hydroxyl group or negative charge were effective in the synthesis of AuNPs, and SS has a high content of these amino acids. Therefore, SS reduced gold ions and induced the synthesis of AuNPs. High-resolution TEM (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA) revealed that SS remained in a form that capped the synthesized AuNPs.

Complex formation in the Fe(II)-Fe(III)-acrylamide–water system and chemical models

This paper investigates complex formation in the Fe(II)-Fe(III)-acrylamide-water system. Dependences of oxidative potentials on the concentration and model parameters of iron acrylamide complexes are discussed. Effect of reaction pH on polymerization of acrylamide and applications of polyacrylamide crosslinking reactions are described. At low pH and high temperatures, formation of water-insoluble cross-linked polymers is possible due to creation of imide bridges between the macromolecules (–CO–NH–CO–). Calculations of the formation constants according to their chemical and physical properties such as pH, temperature and ionic strength of the solution are outlined. Chemical models of acrylamide coordination compounds with Fe(III) and Fe(II) at 298.16 K and energy J = 0.5 are shown in this article. A chemical model of the equilibria numerical values of the complexes for oxidized and reduced forms of the metal, the number of protons they contain, the number of coordinated ligands, hydroxyl groups (g, p, s, l and k), are calculated by comparing the slopes of the experimental curves and partial derivative oxidative potentials of concentration variables. Dependences of the Fe(II) and Fe(III) complexes formation on pH for the systems of Fe(II)-Fe(III)-acrylamide-H2O have been determined.

Production of isofloridoside from galactose and glycerol using α-galactosidase from Alicyclobacillus hesperidum

Isofloridoside (D-isofloridoside and L-isofloridoside) is the main photosynthetic product in red algae. Here, given the importance of isofloridoside, a potentially effective method to produce isofloridoside from galactose and glycerol using whole-cell biocatalysts harboring α-galactosidase was developed. α-Galactosidase-encoding genes from Alicyclobacillus hesperidum, Lactobacillus plantarum, and Bifidobacterium adolescentis were cloned and the proteins were overproduced in Escherichia coli. The α-galactosidase from A. hesperidum (AHGLA) was chosen to synthesize isofloridoside. The effects of reaction pH, temperature, and substrate concentration were investigated. In the optimum biotransformation conditions, the final isofloridoside concentration reached 0.45 M (galactose conversion 23 %). The reaction mixtures were purified using activated charcoal and calcined Celite, and the purified product was identified as a mixture of D- and L-isofloridoside by liquid chromatography-mass spectrometry and nuclear magnetic resonance. This study provides a possible feasible method for the biosynthesis of isofloridoside from low-cost glycerol and galactose.

Modulation of interfacial electrical charges in assembled nano-polyelectrolyte complex of alginate-based macromolecules

pH-sensitive polyelectrolyte complex (PEC) including poly(3-acrylamidopropyl) trimethylammonium chloride/alginate (p(APTMACl)/ALG) was obtained by simple mixing method through electrostatic interactions. Following the synthesis of a cationic polymer p(APTMACl), the effects of reaction pH, ionic strength, polymer concentration and mixing ratio in PEC formation were investigated. UV/Vis, FTIR, AFM, DLS and zeta potential analyses confirmed the formation of PEC. The interaction between p(APTMACl) and ALG has been studied by different variable parameters. Polyelectrolyte complex nanoparticles of p(APTMACl)/ALG with a particle size of 88 nm were formed by the simple mixing of p(APTMACl) (1 mg/mL) and ALG (1 mg/mL) at pH 7. Increasing the alginate concentration led to larger particle size and lower turbidity. The effect of pH, within 1–10 range, on the formation and stability of PEC was studied using UV/Vis spectroscopy. The absorption intensity increased as a function of surface charge of the polymeric chains at pH 7. In the presence of sodium chloride, the electrostatic interactions between two polymers were reduced due to the separation of surface charges by small ions. According to the cytotoxicity analysis for p(APTMACl)/ALG nanoparticles, no toxicity was found on MCF-7 cancer cells by MTT-based assay.

MOFzyme: FJU-21 with Intrinsic High Protease-Like Activity for Hydrolysis of Proteins

In this work, metal-organic frameworks (MOFs) FJU-21 was synthesized by solvothermal method. The crystal structure of FJU-21 was characterized by XRD and BET and it was applied to the catalytic hydrolysis of bovine serum albumin. The effects of reaction pH, temperature and reaction time on the catalytic activity of FJU-21 were studied. FJU-21 were found to possess an intrinsic enzyme mimicking activity similar to that found in trypsin. The Michaelis constant (Km) of the artificial protease (0.18 × 10-3 - 0.20 × 10-3 M-1) was about 15-fold lower than that free trypsin (2.7 × 10-3 M-1) and about 3-fold lower than that of soluble Cu(II) oxacyclen (0.54 × 10-3 M-1). The Kcat of FJU-21 is 102 times higher than that of soluble Cu(II) oxacyclen catalysts and, indicating a much higher affinity of BSA for FJU-21 surface. FJU-21 could be reused for eleven times without losing in its activity.

Effect of Reaction pH on Characterization of Co-precipitated Cobalt ferrite Nanoparticles

Effect of Reaction pH on Characterization of Co-precipitated Cobalt ferrite Nanoparticles

Practical problems when using ABTS assay to assess the radical-scavenging activity of peptides: Importance of controlling reaction pH and time

Effects of reaction pH and time on the antioxidant behaviors of Tyr, Trp, Cys, and their related peptides (Tyr-Gly, Tyr-Glu, Tyr-Lys, Trp-Gly, Trp-Glu, Trp-Lys, Cys-Gly and Cys-Gly) in ABTS assay were investigated. Results showed that all these amino acids and peptides displayed a biphasic kinetic pattern with a fast initial step and a slow secondary step. The initial reaction rates of Tyr, Trp and their related peptides were strongly dependent on pH, while those of Cys and Cys-containing peptides were unaffected by pH. They failed to reach equilibrium over the short incubation period of 6–10min typically used in this assay. Longer incubation time was needed for most of the peptides to approach equilibrium at lower pH. The observed biphasic kinetic pattern as well as the high TEAC values for these amino acids and peptides, could be a result of combined antioxidant behaviors of themselves plus the generated reaction products.

Hb-induced biocatalyzed synthesis of water-soluble polyaniline nanocomposites with controlled handedness in DBSA–CTAB mixed micelle solutions

A new polymerization system for the synthesis of chiral conducting polyaniline (PANI) with high conductivity catalyzed by hemoglobin (Hb) in dodecylbenzenesulfonic acid (DBSA)–cetyltrimethyl ammonium bromide (CTAB) mixed micelle solutions was developed. For the first time, without any other chiral inducer, PANI with controlled handedness was found to be acquired only in the presence of Hb, indicating that Hb played the role of both the inducer and biocatalyst. The effects of reaction pH, concentrations and ratio of the mixed surfactants on the formation of chiral PANI were explored. Results revealed that the conductivity of chiral PANI was closely associated with the molar ratio of DBSA to CTAB. When the ratio of DBSA to CTAB was 3:1, the highest conductivity of 39.71S/cm was obtained. The chiral PANI was characterized by UV–vis absorption spectroscopy, circular dichroism (CD) spectra, Fourier transform infrared spectra (FTIR), field emitted scanning electron microscopy (FESEM) and X-ray diffraction (XRD). Our results demonstrated that this novel system was specific, simple and green, in which the controlled handedness PANI was obtained with various morphologies and high conductivity.

Degradation of methyl orange by UV, O3 and UV/O3 systems: analysis of the degradation effects and mineralization mechanism

The effect of ultraviolet irradiation (UV), ozonation, and the combined UV/O3 systems on the decolorization and degradation of methyl orange, performed in a laboratory-scale reactor, was studied. Decoloration efficiency, UV–vis spectrum, chemical oxygen demand (COD), mass spectrum (MS), and total organic carbon (TOC) analyses were employed. Three oxidative processes including UV, ozonation (O3), and the combined UV/O3 system were assessed to select the most appropriate oxidative process in terms of methyl orange aqueous solution treatment and special emphasis was laid on the effect of reaction pH in the UV/O3 system. The results indicated that the pH value of methyl orange solution decreased with the treatment time, and it reached an acid value when oxidized for 150 min. The COD removal efficiencies of methyl orange were only 46.23 (UV), 44.54 (O3), and 71.17 % (UV/O3) in three processes, while the corresponding decolorization efficiencies were 94.8, 94.2, and 95.1 % after 150 min of treatment. The mineralization mechanism was suggested based on the analysis of the molecular structure of methyl orange, intermediate products, and final products by using MS. For the combined UV/O3 system, the basicity condition was good at the TOC removal.

Removal of rhodamine B by ozone-based advanced oxidation process

The oxidation of rhodamine B in aqueous solution by conventional ozone process and the advanced ozone-based oxidation processes was investigated. The reaction conditions such as ozone dosage, initial concentration of the dye and pH in ozone process were optimized. The decolorization rate of rhodamine B increased with the ozone dosage but decreased with the initial concentration of rhodamine B. Three oxidative processes including UV/ozone, US/ozone and ozone systems were assessed to select the most appropriate oxidative process in terms of rhodamine B aqueous solution treatment and special emphasis was laid on the effect of reaction pH in the three methods. It was found that in all the three methods, the acid condition can promote the oxidation process. The UV/ozone process was the best ozone-based oxidization process, with the decolorization efficiency of 99.78% and COD removal rate of 47.43% after 15 min treatment. The pseudo-first order kinetics was found to fit all the ozone-based processes, with regard to the decoloration and degradation reactions.

Jack bean α-mannosidase digestion profile of hybrid-type N-glycans: Effect of reaction pH on substrate preference

Jack bean α-mannosidase (JBM) is a well-studied plant vacuolar α-mannosidase, and is widely used as a tool for the enzymatic analysis of sugar chains of glycoproteins. In this study, the JBM digestion profile of hybrid-type N-glycans was examined using pyridylamino (PA-) sugar chains. The digestion efficiencies of the PA-labeled hybrid-type N-glycans Manα1,6(Manα1,3)Manα1,6(GlcNAcβ1,2Manα1,3)Manβ1,4GlcNAcβ1,4GlcNAc-PA (GNM5-PA) and Manα1,6(Manα1,3)Manα1,6(Galβ1,4GlcNAcβ1,2Manα1,3)Manβ1,4GlcNAcβ1,4GlcNAc-PA (GalGNM5-PA) were significantly lower than that of the oligomannose-type N-glycan Manα1,6(Manα1,3)Manα1,6Manβ1,4GlcNAcβ1,4GlcNAc-PA (M4-PA), and the trimming pathways of GNM5-PA and GalGNM5-PA were different from that of M4-PA, suggesting a steric hindrance to the JBM activity caused by GlcNAcβ1-2Man(α) residues of the hybrid-type N-glycans. We also found that the substrate preference of JBM for the terminal Manα1–6Man(α) and Manα1–3Man(α) linkages in the hybrid-type N-glycans was altered by the change in reaction pH, suggesting a pH-dependent change in the enzyme–substrate interaction.

Mesoporous silica–magnetite nanocomposites: Fabrication, characterisation and applications in biosciences

Template assisted fabrication of magnetic mesoporous silica–magnetite nanocomposites and their performance in binding and elution of Salmon sperm DNA has been reported. The effect of reaction pH (10–2) during the fabrication of nanocomposites has been studied. All materials fabricated at various pH were characterised by XRD, TEM, FT-IR, nitrogen adsorption and magnetic susceptibility measurements. Fabrication at neutral pH (7) in the presence of a cationic surfactant (cetyl trimethyl ammonium bromide; CTAB) produced core–shell nanocomposites of quasi spherical and rod shaped morphologies with mesoporous (pore size ∼3.5 nm) silica shell and rhombic magnetite core. Fabrication at alkaline pH (10) produced monolithic mesoporous silica composites with embedded magnetite nanoparticles. Fabrication at acidic pH (4 and 2) produced a biphasic mixture of rhombic magnetite and amorphous silica rods. A similar fabrication at acidic pH (2) in the absence of CTAB produced a biphasic mixture of rhombic magnetite and spherical silica nanoparticles. All materials exhibited a high value of Salmon sperm DNA binding at physiological pH whereas elution value of DNA was observed to be dependent on the extent of silica coating on magnetite nanoparticles.

Degradation of a commercial textile biocide with advanced oxidation processes and ozone

The occurrence of significant amounts of biocidal finishing agents in the environment as a consequence of intensive textile finishing activities has become a subject of major public health concern and scientific interest only recently. In the present study, the treatment efficiency of selected, well-known advanced oxidation processes (Fenton, Photo-Fenton, TiO 2/UV-A, TiO 2/UV-A/H 2O 2) and ozone was compared for the degradation and detoxification of a commercial textile biocide formulation containing a 2,4,4′-trichloro-2′-hydroxydiphenyl ether as the active ingredient. The aqueous biocide solution was prepared to mimic typical effluent originating from the antimicrobial finishing operation (BOD 5,o⩽5 mg/L; COD o=200 mg/L; DOC o (dissolved organic carbon)=58 mg/L; AOX o (adsorbable organic halogens)=48 mg/L; LC 50,o (lethal concentration causing 50% death or immobilization in Daphnia magna)=8% v/v). Ozonation experiments were conducted at different ozone doses (500–900 mg/h) and initial pH (7–12) to assess the effect of ozonation on degradation (COD, DOC removal), dearomatization (UV 280 and UV 254 abatement), dechlorination (AOX removal) and detoxification (changes in LC 50). For the Fenton experiments, the effect of varying ferrous iron catalyst concentrations and UV-A light irradiation (the Photo-Fenton process) was examined. In the heterogenous photocatalytic experiments, Degussa P25-type TiO 2 was used as the catalyst and the effect of reaction pH (3, 7 and 12) and H 2O 2 addition on the photocatalytic treatment efficiency was examined. Although in the photochemical (i.e. Photo-Fenton, TiO 2/UV-A and TiO 2/UV-A/H 2O 2) experiments appreciably higher COD and DOC removal efficiencies were obtained, ozonation appeared to be equally effective to achieve dearomatization (UV 280 abatement) at all studied reaction pH. During ozonation of the textile biocide effluent, AOX abatement proceeded significantly faster than dearomatization and was complete after 20 min ozonation (267 mg O 3). On the other hand, for complete detoxification, ozonation had to be continued for at least 30 min (corresponding to 400 mg O 3). Effective AOX and acute toxicity removal was also obtained after heterogeneous photocatalytic treatment (TiO 2/UV-A and TiO 2/UV-A/H 2O 2). The Fenton-based treatment experiments and particularly the dark Fenton reaction resulted in relatively poor degradation, dearomatization, AOX and acute toxicity removals.

Photochemical oxidation of reactive azo dye with UV–H 2O 2 process

The photooxidation of a chlorotriazine reactive azo dye Reactive Orange 4 has been carried out in the presence of H 2O 2 using UV-A light. The effects of reaction pH, applied H 2O 2 dose, UV light power have been studied. These parameters strongly influence the decolourisation and degradation. The increase of initial dye concentration decreases the removal rate. The kinetics of decolourisation and degradation follow pseudo-first order. The solar–H 2O 2 process is also able to oxidise the dye and its efficiency is comparable with UV–H 2O 2. The influence of dye assisting chemicals such as NaOH, NaCl and Na 2CO 3 on photodecolourisation has been investigated. Addition of these chemicals inhibit the removal rate. The optimum operating conditions of the method are reported.

Effect of reaction pH on the photodegradation of model melanoidins

The effect was studied of the pH of the amino-carbonyl reaction on the photodegradation of model melanoidins. Nondialyzable model melanoidins were prepared from glucose and lysine with or without initial pH control to 7.0.: 2 mol/l phosphate buffer (buffer-melanoidin) and pH adjustment at the reaction start with NaHCO 3 (NaHCO 3-melanoidin). Melanoidin was also prepared from glucose and the lysine–Cu 2+complex to investigate the difference of complexes between melanoidin and Cu 2+ (Cu 2+-melanoidin). Each melanoidin solution was irradiated with a Xe or tungsten-halogen lamp under dissolved oxygen or by the continuous supply of oxygen in a Cu 2+/O 2 or ascorbic acid/Cu 2+/O 2 system. The effects of the concentrations of Cu 2+ and melanoidin, reaction pH value, and metal ion species on the decolorization rate in the Cu 2+/O 2 system were investigated. The most effective factor for decolorization was found to be the melanoidin concentration. The decolorization rate was negligible when 14 g/l of Cu 2+-melanoidin was photodegraded in the ascorbic acid/Cu 2+/O 2 system under dissolved oxygen, although depolymerization was observed. Photodegradation of NaHCO 3-melanoidins in the Cu 2+/O 2 system by the continuous supply of oxygen resulted in an increased decolorization rate, decreased molecular mass, production of low-molecular-weight compounds, release of free lysine, and pI change. The buffer- and Cu 2+-melanoidins did not show changes in chemical characteristics similar to those of the NaHCO 3-melanoidin.

Advanced oxidation of a reactive dyebath effluent: comparison of O3, H2O2/UV-C and TiO2/UV-A processes

In the present study the treatment efficiency of different AOPs (O3/OH−, H2O2/UV-C and TiO2/UV-A) were compared for the oxidation of simulated reactive dyebath effluent containing a mixture of monochlorotriazine type reactive dyes and various dye auxiliary chemicals at typical concentrations encountered in exhausted reactive dyebath liquors. A525 (color), UV280 (aromaticity) and TOC removal rates were assessed to screen the most appropriate oxidative process in terms of reactive dyebath effluent treatment. Special emphasis was laid on the effect of reaction pH and applied oxidant (O3, H2O2) dose on the observed reaction kinetics. It was established that the investigated AOPs were negatively affected by the Na2CO3 content (=867mg/L) which is always present at high concentrations in dyehouse effluents since it is applied as a pH buffer and dye fixation agent during the reactive dyeing process. The ozonation reaction exhibited almost instantaneous decolorization kinetics and a reasonable TOC reduction rate. It appeared to be stable under the investigated advanced oxidation conditions and outranked the other studied AOPs based on the above mentioned criteria. Besides, the electrical energy requirements based on the EE/O parameter (the electrical energy required per order of pollutant removal in 1m3 wastewater) was calculated for the homogenous AOPs in terms of decolorization kinetics. In view of the electrical energy efficiency, ozonation and H2O2/UV-C oxidation at the selected treatment conditions appear to be promising candidates for full-scale dyehouse effluent decolorization.